1. Field Of The Invention
The present invention relates to a method and apparatus for rolling a metal workpiece by means of work rolls having a cylindrical portion and a tapered portion.
2. Description of The Prior Art
It has been known to provide a workpiece of given width by longitudinal slitting of the edges. This, however, can produce substantial scrap.
It has also been known in connection with the rolling of metal slabs to provide an initial profile from the sizing pass wherein the central portion of the slab is of reduced thickness with respect to the generally transversely outwardly diverging lateral portions thereof. Subsequently, the workpiece is rotated 90 degrees and is run through a rolling mill stand which provides a generally uniform thickness to the workpiece. The workpiece is subsequently rotated 90 degrees in the opposite direction from the initial rotation and further rolling is effected so as to provide a workpiece of desired uniform thickness. This practice is known as "broadsiding". See generally U.S. Pat. Nos. 4,238,946 and 4,392,371. One of the difficulties with this practice is the need to effect two 90 degree rotations of the workpiece.
U.S. Pat. No. 3,857,268 discloses axially shiftable tapered work rolls employed to accommodate varying workpiece width and improve flatness control; See also Japan No. 59-110401 and Japan No. 58-53384. These approaches do not employ the method for spreading the workpiece.
In spite of these known practices, there remains a need for a more efficient, more direct method and associated apparatus for effecting rolling of a plate of a desired thickness.